It is often said half-teasingly that canvassers and pollsters are more likely to meet Labour voters than Tories because Tory voters are still at work. Now there is empirical evidence for the claim. Professor John Curtice, perhaps the only pollster with his reputation intact after he called the 2015 election, says there is no such thing as “shy” Tories skewing polls, they are just “busy“. Curtice’s study found that if polls were based on people who answered the door on a first visit, Labour would be six points ahead. If polls were based on those who needed three to six visits before answering, the Tories had an 11 point lead. His conclusion: Labour voters were more likely to be at home rather than out at work.

“Conservatives are just simply more difficult to get hold of. There is an availability bias. People who you can get hold of first time round, who say, ‘oh yes come in’ are disproportionately Labour voters. The people you can easily get hold of are not representative.”